Oct. 31, 1889] 



NATURE 



645 



the rabbit, or the guinea-pig. The frog is a very aberrant 

 member of the Batrachia, and it would be very instructive 

 for the student to examine a more typical representative of 

 the class. Such a one is the American Proteus {Necturus 

 maatlatus, Ref.), used at Cornell University, Ithaca, N.Y. 

 During the last few years I have received many specimens of 

 Vertebrates from two fishermen — Mr. Russell Dee and Mr, F. 

 C. Audibert, from Marietta, Ohio. Lately, Mr. Audibert has 

 written to me that he could procure any quantity of material, 

 if wanted, and he would charge only 25 cents, (a little over one 

 shilling) for each specimen. From the list of specimens sent to 

 me by Mr. Audibert I select the following, which appear the 

 most important for laboratory use : — 



Accipenser mactilostis, Les. 

 Polyodon folium, Lat. 

 Lepidosteus osseus, L. 

 Necturus viaculosus, Ref. 

 MenopoJ}ia alleghaniensis, Daud. 

 Irionyx nmticus, Les. 



The instructive value of these specimens is certainly very 

 great, and the low price could enable any biological laboratory 

 to secure this material. G. Baur. 



New Haven, Conn., September 30. 



" Darwinism." 



It has now become to me a matter of amusement to note how 

 those naturalists who of late years have drifted most widely from 

 the doctrines of evolution as these were held by Darwin, habitu- 

 ally accuse me of Darwinian heresy because I have not seen any 

 adequate reason to depart from those doctrines in their entirety. 

 Perceiving that there has been some change of relative position, 

 while failing to perceive that the movement has been altogether on 

 their own side, these naturalists represent that I have been fall- 

 ing away from Darwinism, when the fact is that they have been 

 advancing beyond anything that was ever countenanced by the 

 judgment of Darwin — and even expressly accepting the view 

 which he so vehemently rejected, viz. that of regarding natural 

 selection as the sole cause of organic evolution. Thus, for 

 example, when in Nature of October 10 (p. 569) Prof Ray 

 Lankester gravely designates my paper on physiological selec- 

 tion a "laborious attack upon Darwin's theory of the origin of 

 species," it becomes evident how fast and far he has travelled 

 from his Darwinism of two or three years ago. For, to put it 

 briefly, unless it can be shown that Darwin considered natural 

 selection the only possible cause of organic evolution, and did 

 not consider sterility between allied species as probably due to 

 some other principle of change, it is obvious that there can be 

 nothing in my "additional suggestion on the origin of species " 

 which may in any sense be designated an attack upon the dis- 

 tinctively Darwinian theory. Yet it is with regard to these very 

 points that the opinion of Darwin was steadily opposed to that 

 of Wallace ; i.e. to the present opinion of Lankester. Therefore, 

 quite apart from any question touching the truth of this "addi- 

 tional suggestion" or "supplementary hypothesis" (which, 

 however, I may here parenthetically remark, will soon be shown 

 to be in no way seriously affected by Mr. Wallace's sole remain- 

 ing criticism), it is sufficiently evident that, when the object of 

 publishing the hypothesis was expressly and i-epeatedly stated to 

 have been that of meeting the main difficulties which had been 

 advanced against the theory of natural selection, the present 

 designation of this hypothesis as an elaborate attack upon that 

 theory is simply absurd. 



But my object in now writing is to state, apropos of Prof. 

 Lankester's remarks on the inadequacy of Mr. Wallace's criti- 

 cism of Mr. Gulick's paper, that I have just received a commu- 

 nication from the latter gentleman (who writes from Japan), 

 requesting me to exercise my discretion as to publishing in these 

 columns a reply to that criticism. Unfortunately this reply is 

 too long for insertion, and as I do not see how it can be curtailed 

 without serious detriment, I have refused to incur the responsi- 

 bility of publishing it in an abbreviated form. At the same time 

 it seems but just to let the readers of Nature know that a full 

 reply to Mr. Wallace's criticisms (in these columns and else- 

 where) has been prepared ; since otherwise the silence of its 

 author might be misinterpreted. 



To me it appears that Mr. Gulick's work is much the most 

 profound that has ever been published on the important 

 matters of which it treats (viz. isolation in all its forms, with its 

 consequences in "segregate breeding" and "divergent evolu- 



tion ") ; and therefore I am glad to take this opportunity of 

 recognizing his priority, by some fifteen years, in thinking out, 

 and largely verifying by his researches on land shells, the theory 

 of physiological selection. George J. Romanes. 



Geanies, Ross-shire, October 12. 



Sunset Glows. 



It is a curious fact that a revival of sunset-glows, similar to 

 those described by Sereno E. Bishop in a letter published in 

 Nature for August 29 (p. 415), was observed in Western New 

 York at almost precisely the same time that he saw them at 

 Honolulu. I inclose a clipping from the Rochester (N.Y.), 

 I Democrat and Chronicle, which was published on July 21 : — 

 j "The skies at evening show signs of the gradual return of 

 the red light. It will be of interest to ascertain if the pheno- 

 menon reappears as the solar disturbances continue to increase 

 in energy to the maximum. It is quite apparent now that the 

 minimum has been passed, and the tendency is toward an increase 

 in the number and in the violence of solar disturbances. There 

 are certainly three and probably four well-defined disturbances 

 at present." M. A. Veeder, 



Lyons, New York, September 13. 



" The Teaching of Science." 



I BEG that the following alterations may be made in the 

 " Suggestions for a Course of Elementary Instruction in Physical 

 Science," printed in Nature of October 17. 



Henry E. Armstrong, 



P, 602, Problem II,, line li from above, read "by means of 

 iron " instead of "by means of phosphorus." 



P. 603, Problem VII., line 20 from below, instead of "when 

 metals are heated with acids," read " when metals are dissolved 

 in acids." 



P. 604, Problem IX., line 31 from above in right-hand 

 column, read "dried hydrogen," instead of "dried oxygen." 



P. 605, Problem XII., line 17 from above in right-hand 

 column, read "zinc oxide," instead of "lime oxide." 



TELESCOPES FOR STELLAR PHOTOGRAPHY} 

 II. 



IN considering the essentials of a good systeni of control 

 for equatorial clocks, it is necessary to keep in view the 

 exact conditions required. It is not sufficient that the con- 

 trolling apparatus (of whatever form it may be) should 

 simply bring the rate of the clock, which has been inter- 

 fered with by some adventitious disturbance, correct once 

 more ; it must do more, it must correct this error. For, 

 suppose a star be set on the slit of a spectroscope, and the 

 clock started, and say, as in Dr. Muggins's case, a photo- 

 graphic plate inserted for a two hours' exposure. Now 

 suppose that five minutes after the commencement of the 

 exposure, an error of one-tenth or two-tenths of a second 

 occurs from some disturbing cause (a fragment of dirt on 

 the tooth of a wheel, or other cause) ; if the controlling 

 apparatus be of such a nature as simply to bring the 

 clock-rate correct again, the position of the telescope will 

 be the above quantity, one-tenth or two-tenths of a second, 

 in error for the remainder of the exposure, although the 

 rate may be absolutely correct for the whole times. In 

 other words, the star will have moved off the slit, by a 

 quantity equivalent to what the instrument would move in 

 one-tenth or two-tenths of a second, and will continiie off 

 the slit for the remainder of the two hours. So it will be 

 seen that no controlling apparatus is of any use whatever, 

 unless, as well as keeping the rate uniform, it corrects the 

 errors that have crept in. In consequence of not keeping 

 this point in view, many most ingenious but useless ar- 

 rangements have been from time to tinle proposed. A 

 little consideration will show that this arrangement meets 

 all requirements. 

 The above arrangement is somewhat similar to Dr. Gill s. 



' A Paper read by Sir Howard Grubb, F.R.S., before the Society of Arte, 

 on April 18, 1888. Continued from p. 444- 



